Conceptual design of a high-sensitivity small animal PET camera with 4π coverage

We present a conceptual design of a high-sensitivity PET camera that completely encloses a small animal in a rectangular volume formed by 6 planar banks of detector modules. The 4 pi geometry and 3 attenuation-length fast scintillators provide significantly higher sensitivity than contemporary animal PET cameras, while the depth of interaction (DOI) measurement and small crystal width achieve isotropic, high spatial resolution. The absolute sensitivity is 24 kcps/mu Ci, similar to 120 times higher than contemporary systems; the true event count rate is increased by covering 10 times the solid angle using 80% efficient detectors. For a 29 g "mouse", the total scatter event rate is 11% of the total true event rate. A short (2 nsec) coincidence window and the absence of out of field activity implicit with whole animal coverage yield a small random fraction. Assuming a maximum system count rate of 10 Mcps (achievable with electronics under development), the noise equivalent count rate as a function of activity concentration has a maximum of 6.6 Mcps at 25 mu Ci/cc. 2D reconstruction algorithms indicate a spatial resolution of 2.3 mm fwhm through most of the field of view.